Roll clutch starter drive with shock absorber

ABSTRACT

A ROLL CLUTCH STARTER DRIVE IS PROVIDED WITH A COMPRESSIBLE CUSHION MEMBER COMPRESSED BY AXIAL TRANSLATION OF A SPLINED SLEEVE TO REDUCE THE PEAK TORQUE APPLIED TO THE COMPONENTS OF THE STARTER DRIVE AND TO EXTEND THE SERVICE LIFE OF THE STARTER MOTOR AND DRIVE.

Nov. 2, 1971 P. PATCHETT 3,615,700

ROLL CLUTCH STARTER DRIVE WITH SHOCK ABSORBER Filed Oct. 31, 1969 mw WvWM lNVIiN'H )R. fwocmw QMA @Q. m

ATTORNEY WW QR Q NW United States Patent O 3,616,700 ROLL CLUTCH STARTERDRIVE WITH SHOCK ABSORBER Philip L. Patchett, Horseheads, N.Y., assignorto The Bendix Corporation Filed Oct. 31. 1969, Ser. No. 872,908 Int. Cl.F02n 15/06 US. Cl. 74-7 R 7 Claims ABSTRACT OF THE DISCLOSURE A rollclutch starter drive is provided with a compressible cushion membercompressed by axial translation of a splined sleeve to reduce the peaktorque applied to the components of the starter drive and to extend theservice life of the starter motor and drive.

BACKGROUND OF THE INVENTION Field of the invention The present inventionrelates to the art of coupling motors to internal combustion engines forrotary starting of the internal combustion engine, and particularly tothat class of starter drives termed roll clutch starter drives.

Prior art The evolution of internal combustion engines and the startingsystems used in conjunction therewith has established two criteria forthe starter drives which interface between the starting system and theinternal combustion engine which can currently be met by only one typeof starter drive. The roll clutch starter drive is the only type ofstarter drive which provides the quiet operation and low wear resultingin long life suited to automotive use. However, as the evolution ofinternal combustion engines has produced a steady increase in the size(displacement) of the engines, the performance demands placed on thestarting system have also increased. The torque output of the startingmotor has been steadily raised so as to provide sufficient torque,termed stall torque, to initiate movement of the ring gear of theinternal combustion engine yet the roll clutch starter drive has notgrown in size and as a consequence, has been less and less able toaccommodate the high peak, or reaction torques which are developed as aresult of the increased engine sizes. Starter drives, other than rollclutch starter drives, which are able to efliciently handle these torquelevels are currently unacceptable for domestic automotive applicationbecause of their high initial cost, high wear rate, and the high noiselevels generated when in operation. The roll clutch starter drive, onthe other hand, is relatively quiet in operation has low wear rates,occupies less space, and is less expensive making it the preferredstarter drive.

The roll clutch starter drives rely upon the natural resiliency of theouter race member, rollers, and inner race surfaces in the roll clutchto absorb the peak torques to which the starting system is subjected.Peak torque is that torque which must be absorbed by the starting systemdue to the fact that energy developed within the system as the startingmotor accelerates the pinion into mesh with the ring gear must bedissipated when the starter motor speed is rapidly decelerated as aconsequence the rest condition of the ring gear. However, as the peaktorques increase, the chances of an early metal fatigue failure increasecausing the life expectancy of the roll clutch starter drives to dropquite drastically. While these drives are individually inexpensive, theneed for their replacement at a comparatively early date makes theirtotal cost unattractive. It is, therefore, an object of the presentinvention to provide an improved roll clutch starter drive having anextended life potential. It is a further object of the pres- 'ice entinvention to provide a roll clutch starter drive having a high stalltorque characteristic and a low peak torque characteristic. It has beenfound that a slight reduction of peak torque will greatly increase theservice life of the device. It is, therefore, an object of the presentinvention to provide a roll clutch starter drive having a lower peaktorque characteristic than roll clutch starter drives of comparable sizeand torque transmitting capability.

SUMMARY OF THE PRESENT INVENTION In a roll clutch starter driveaccording to the present invention, a sleeve member is situatedintermediate the outer race of the roll clutch and the shaft of thestarter motor and is interconnected to each by a pair of splineconnections. The spline connections are biased to axially opposedextremes when the starter system is not energized. Resilient means areprovided in biasing one of the spline connections to permit telescopingmovement of one of the spline connections in opposition to the resilientbias when a peak torque situation is encountered to thereby absorb aportion of the peak torque and, therefore, reduce the peak torqueapplied to the system. The resilient means are arranged to maintain oneof the spline connections relatively immovable until a peak torque isencountered and then to control relative movement of the splines.

BRIEF DESCRIPTION OF THE DRAWING The single figure of the drawingillustrates the present invention as applied to a starting system usinga positive shift roll clutch starter drive.

DETAILED DESCRIPTION Referring now to the drawing, the present inventionis illustrated with regard to a positive shift starting system 10. Thestarter drive 12 is mounted on shaft 14 of a starter motor means, shownfragmentarily at 16, having a casing 18. The drive 12 is shifted onshaft 14 into and out of engagement with the ring gear 20 of an engineto be started, not shown, by advancement means shown here as shiftinglever 22. The shifting lever 22 may be controlled in the usual manner,as by a solenoid, and is intended to be also illustrative of shiftadvancement means and mechanisms such as those illustrated in UnitedStates Letters Patent 3,299,719, issued in the name of P. Toulier andUnited States Letters Patent 3,465,353, issued in the name of J. E.Buxton et al.

The starter drive 12 is comprised of the ring gear engaging pinion 24which is connected to the uni-directional roll clutch 26, the shockabsorbing means 28 and the coupling member or sleeve 30 coupled to theshaft 14. The pinion 24 is connected to the inner race 32 of the rollclutch 26 while the outer race 34 is coupled by spline connection 36 tothe sleeve 30. The shock absorber is comprised of cup shaped retainermeans or member 38, resilient shock absorbing member 40 and rigidabutment member 42. The resilient shock absorbing member is, in thepreferred embodiment, a compressible annulus of resilient material suchas rubber, but other materials and other configurations are possible.The shock absorber means 28 is arranged to bias the spline connection 36in a direction of maximum extension so that the outer race 34 and hence,the pinion 24, is at its axially rightmost extreme position relative tothe sleeve member 30. Abutment member 42 is axially positioned, relativeto the coupling member 30, by the resilient means 40 and lock ring 44and the resilient means 40 are operative to bias retainer means 38 intoaxial abutment with the outer race 34 of the roll clutch means 26 toprovide an axially fixed connection therewith.

Sleeve member 30 is coupled to the shaft 14 through a second splineconnection 46. When the drive is not in use, the spline connection 46 isbiased in a direction of minimum extension by means shown here as theshift lever 22. Spline connection 46 is shown as a helical spline sincea suitably directed helical spline connection between the shaft 14 andstarter drive 12 will aid meshing between the pinion 24 and ring gear 14through screwjack action.

At least one of the spline connections 36, 46 must be a helical splineso that a peak torque condition can generate an axial thrust, throughscrew-jack action, sufficient to act against the bias applied by theresilient means 40'. The other of the spline connections should notinhibit the sliding movement required to act against the bias of theresilient means 40. It has been determined that the second splineconnection may be a straight or helical spline, and if helical, may beof variable lead and of the same or opposite direction as the firstspline connection. Lead in this instance should be understood to meanthe axial length of a shaft required for a spline to make one completeturn around the shaft, with a straight spline having infinite lead.

OPERATION Under comparatively low torque situations, the shock absorbermeans 28 and the spline connection 36 behave as an axially solidconnection between the outer race 34 of the roll clutch and the sleevemember 30. Immediately following engagement of the ring gear 20 by thepinion 24, the amount of torque being transmitted through the starterdrive will begin to rise to a high peak value due to the high speed ofthe starter motor and the at rest inertia of the engine. In the priorart type of drive, the peak could easily exceed 100 lb. ft. of torque.This would tend to cause a slight elastic deformation of the roll clutch26 and particularly of the outer race member 34. This would eventuallylead to a metal fatigue failure of the roll clutch rendering the deviceinoperative and necessitating a time consuming, inconvenient, andexpensive repair. For larger displacement engines, the peak torques areproportionally higher but the fatigue factors increase as multiplesthereby reducing the statistical life of the drive by factors as high as10. However, with a roll clutch drive according to my invention and uponthe occurrence of a peak torque condition, the resilient means 40 willbe acted upon by the rigid member 42 and by cup member 38 to absorbenergy when torque begins to peak. This serves to reduce or eliminatethe peak torque levels.

As rotating pinion 24 engages the stationary ring gear 20, the rotationof the pinion 24 and of the starter drive 12 relative to the shaft 14will be impeded. This will generate a rightward thrust, relative to thedrawing, on the starter drive 12 as a result of the screw-jack action atthe helical spline connection 46. The drive will be rapidly urged intofull engagement of the pinion 24 with the ring gear 20 until pinion 24abuts the stop means 48 on the shaft 14. Since the drive 12 can nolonger advance, the drive will attempt to rotate with the shaft. Becausethe ring gear 20 has a high moment of inertia and will attempt to remainstationary, a peak torque situation is encountered. At some selectablyhigh torque level, the axial thrust on the sleeve 30 as a result of thescrewjack action at the spline connection 46 will be sufiicient toovercome the bias of the resilient means 40 and the sleeve 30 will againadvance rightward causing a deformatiog of the resilient member 40. Theresilient member 40 is, in this instance, a compressible annulus ofrubber or the like material. As the resilient member is compressed, thespline connection 36 will begin to telescope. As the resilient member 40continues to be compressed, the amount of torque applied to the rollclutch, and therefore, available to subject the roll clutch to metalfatigue situations, will be substantially reduced. Depending upon theresiliency of the compressive member 40, the torque value at whichcompression occurs can be controlled and a substantial increase instarter drive life can be achieved. For instance, I have found that peaktorque in two other- 4 wise identical starter drives can be reduced fromabout 122 lbs. ft. to about 92 lbs. ft. (a reduction of 25%) through thepractice of my invention with spline connection 46 being helical andspline connection 36 being straight.

Virtually any combination of spline connections may be used in thepractice of my invention. However, the best results which I haveobtained have been obtained with a comparatively short lead in thespline connection 46 between the shaft 14 and the sleeve 30 and aslightly longer lead in the spline connection 36 between the sleevemember 30 and the outer race 34 of the roll clutch and both splineconnections were in the same direction. This is believed to occur as aresult of improved mechanical advantage serving to initiate compressionof the resilient member at lower torque-levels so that greater amountsof torque energy are absorbed thereby further lowering peak torque. Inone instance, reduction of the lead of spline connection 46 from 16inches to 6 inches in a starter drive according to my invention servedto produce a further reduction in peak torque of 15% (based on theinitial figure of 122 lbs. of torque).

I claim:

1. In combination with a roll clutch starter drive of the type having apinion, a uni-directional roll clutch means, advancement means operativeto advance the pinion into engagement with the ring gear of an engine tobe started and coupling means operative to provide a means forconnecting the starter drive to a source of rotary power, theimprovement comprising shock absorbing mean-s interconnecting said rollclutch means and said coupling means operative to provide an axiallysubstantially rigid connection therebetween at levels of transmittedtorque below a predeterminable level and further operative to deform andthereby absorb torque at torque levels above the predeterminable level,said coupling means comprising a sleeve member having splines adaptedfor coacting with mating splines on a rotary shaft of a starter motormeans, the starter motor means being the source of rotary power, andsaid shock absorbing means comprising resilient means, means providing asubstantially axially fixed connection between said resilient means andsaid sleeve means and means providing a substantially axially fixedconnection between said resilient means and said roll clutch means, saidresilient means being deformable to vary the axial relationship betweensaid sleeve member and said roll clutch means.

2. In combination with a roll clutch starter drive of the type having apinion, a uni-directional roll clutch means, advancement means operativeto advance the pinion into engagement with the ring gear of an engine tobe started and couplig means operative to provide a means for connectingthe starter drive to a source of rotary power, the improvementcomprising shock absorbmg means interconnecting said roll clutch meansand said coupling means operative to provide an axially substantiallyrigid connection therebetween at levels of transmitted torque below apredetermined level of torque and further operative to deform and absorbtorque at torque levels above the predetermined level, said shockabsorbing means comprising resilient means providing an axially variableconnection between said coupling means and said roll clutch means, saidresilient means requiring a generated force above a predeterminedminimum prior to variation of said axially variable connection, saidminimum generated force being indicative of torque above a selectedlevel, said resilient means comprising fixed means connected to saidcoupling means, retaining means, and a resilient member confined betweensaid fixed means and said retaining means and operative to bias saidretaining means into an abutting relationship with said roll clutchmeans, and said coupling means are connected to said roll clutch meansby splines and said resilient means are operative to urge said rollclutch means toward a position of maximum axial extension.

3. A starter drive comprising:

coupling means adapted for connection to the output shaft of a motormean-s;

pinion means adapted for engagement with the ring gear of an engine tobe started;

roll clutch means connected to said pinion means operative to provide auni-directional torque transmitting connection between said couplingmeans and said pinion means; and

resilient means interconnecting said roll clutch means and said couplingmean-s operative to be deformed when the level of transmitted torqueexceeds a selected value;

said coupling means being connected to said roll clutch means bysplines; and

said resilient means operative to yieldably bias said roll clutch meansto a position of maximum axial extension of said roll clutch meansrelative to said coupling means.

4. The starter drive as claimed in claim 3 wherein said coupling meanscomprise an axially-extended sleeve member and including further:

abutment means arranged for cooperation with said sleeve member andresilient means and operative to establish an axially fixed position ofsaid resilient means relative to said sleeve member;

said resilient means engaging said abutment means and operative to urgesaid sleeve member toward said fixed position; and

retainer means engaging said roll clutch means and engaging saidresilient means whereby said resilient means are confined between saidretainer means and said abutment means.

5. In combination with a starter drive of the type having a pinion, aradially acting uni-directional clutch means, advancement meansoperative to advance the pinion into engagement with the ring gear of anengine to be started and coupling means operative to provide a means forconnecting the starter drive to a source of rotary power, theimprovement comprising shock absorbing means interconnecting said clutchmeans and said coupling means operative to provide an axiallysubstantially rigid connection therebetween at levels of transmittedtorque below a predetermined level and further operative to deform andthereby absorb torque at torque levels above the predeterminable level,said coupling means comprising a sleeve member having splines adaptedfor coacting with mating splines on a rotary shaft of a starter motormeans, the starter motor means being the source of rotary power, andsaid shock absorbing means comprising resilient means, means providing asubstantially axially fixed connection between said resilient means andsaid sleeve means and means providing a substantially axially fixedconnection between said resilient means and said clutch means, saidresilient means being deformable to vary the axial relationship betweensaid sleeve member and said clutch means.

6. A starter drive comprising:

coupling means adapted for connection to the output shaft of a motormeans;

pinion means adapted for engagement with the ring gear of an engine tobe started;

radially acting clutch means connected to said pinion means operative toprovide a uni-directional torque transmitting connection between saidcoupling means and said pinion means; and

resilient means interconnecting said clutch means and said couplingmeans operative to be deformed when the level of transmitted torqueexceeds a selected value;

said coupling means connected to said clutch means by splines; and

said resilient means operative to yieldably bias said clutch means to aposition of maximum axial extension of said roll clutch means relativeto said coupling means.

7. The starter drive as claimed in claim 6 wherein said coupling meanscomprise an axially-extending sleeve member and including further:

abutment means arranged for cooperation with said sleeve member andresilient means and operative to establish an axially fixed position ofsaid resilient means relative to said sleeve member;

said resilient means engaging said abutment means and operative to urgesaid sleeve member toward said fixed position; and

retainer mean-s engaging said roll clutch means and engaging saidresilient means whereby said resilient means are confined between saidretainer means and said abutment means.

References Cited UNITED STATES PATENTS 2,455,328 11/1948 Buxton 74-7 X2,939,323 6/1960 Kochendorfer 74-6 MILTON KAUFMAN, Primary Examiner

